<template>
    <canvas id="s-canvas" :width="contentWidth" :height="contentHeight">
    </canvas>
</template>
<script>
export default {
    name: 'SIdentify',
    props: {
      identifyCode: {
       type: String,
       default: '1234'
      },
      fontSizeMin: {
       type: Number,
       default: 35
      },
      fontSizeMax: {
       type: Number,
       default: 60
      },
      backgroundColorMin: {
       ype: Number,
       default: 180
      },
      backgroundColorMax: {
       type: Number,
       default: 240
      },
      colorMin: {
       type: Number,
       default: 50
      },
      colorMax: {
       type: Number,
       default: 160
      },
      lineColorMin: {
       type: Number,
       default: 40
      },
      lineColorMax: {
       type: Number,
       default: 180
      },
      dotColorMin: {
       type: Number,
       default: 0
      },
      dotColorMax: {
       type: Number,
       default: 255
      },
      contentWidth: {
       type: Number,
       default: 160
      },
      contentHeight: {
       type: Number,
       default: 60
      }
    },
    methods: { // 生成一个随机数    
        randomNum(min, max) {
            return Math.floor(Math.random() * (max - min) + min)
        },
        // 生成一个随机的颜色
        randomColor(min, max) {
            let r = this.randomNum(min, max)
            let g = this.randomNum(min, max)
            let b = this.randomNum(min, max)
            return 'rgb(' + r + ',' + g + ',' + b + ')'
        },
        drawPic() {
            let canvas = document.getElementById('s-canvas')
            let ctx = canvas.getContext('2d')
            ctx.textBaseline = 'bottom'
         // 绘制背景
            ctx.fillStyle = this.randomColor(
            this.backgroundColorMin,
            this.backgroundColorMax)
            ctx.fillRect(0, 0, this.contentWidth, this.contentHeight)
        // 绘制文字
            for (let i = 0; i < this.identifyCode.length; i++) {
                this.drawText(ctx, this.identifyCode[i], i)
            }
            this.drawLine(ctx)
            this.drawDot(ctx)
        },
        drawText(ctx, txt, i) {
            ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax)
            ctx.font = this.randomNum(this.fontSizeMin, this.fontSizeMax) +'px SimHei';
            let x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
            let y = this.randomNum(this.fontSizeMax,this.contentHeight - 5)
            let deg = this.randomNum(-45, 45)
     // 修改坐标原点和旋转角度 
            ctx.translate(x, y)
            ctx.rotate(deg * Math.PI / 180)
            ctx.fillText(txt, 0, 0)
     // 恢复坐标原点和旋转角度
            ctx.rotate(-deg * Math.PI / 180)
            ctx.translate(-x, -y)
        },
        drawLine(ctx) {
     // 绘制干扰线 
            for (let i = 0; i < 8; i++) {
                ctx.strokeStyle = this.randomColor(this.lineColorMin, this.lineColorMax)
                ctx.beginPath()
                ctx.moveTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
                ctx.lineTo(this.randomNum(0, this.contentWidth),this.randomNum(0, this.contentHeight))
                ctx.stroke()
            }
        },
        drawDot(ctx) {
     // 绘制干扰点  
            for (let i = 0; i < 100; i++) {
                ctx.fillStyle = this.randomColor(0, 255)
                ctx.beginPath()
                ctx.arc(this.randomNum(0, this.contentWidth),this.randomNum(0, this.contentHeight), 1, 0, 2 * Math.PI)
                ctx.fill()
            }
        }
    },
    watch: {
        identifyCode() {
            this.drawPic()
        }
    },
    mounted() {
        this.drawPic()
    }
}
</script>
